Along with the recent world-wide tendency toward exhaustion of petroleum resources, the general attention is given to shale oil available from oil shale existent underground in large quantities as a new fuel oil. However, since shale oil is contained in oil shale in only such a small amount as for example about 60 kg per ton of oil shale, industrial distillation of shale oil from oil shale requires huge distilling facilities. There is therefore a demand for developing a method for efficiently distilling shale oil from oil shale.
The methods for distilling shale oil from oil shale now in operation in an industrial scale or considered to be in operation in the future in an industrial scale may be broadly classified into the following three types, depending upon the means for supplying the heat for distillation:
(1) with the heat of fuel burning in the distilling furnace; PA1 (2) with the heat of a high-temperature granular heat medium supplied into the distilling furnace; and, PA1 (3) with the heat of a high-temperature gaseous heat medium blown into the distilling furnace. PA1 whereby a high-temperature gas blown through said gas blowing port into an oil shale distilling chamber passes horizontally through said plurality of vent apertures of said two vertical partitions and through said oil shale in said oil shale treating chamber, thereby an oil shale being preheated in said oil shale preheating chamber, and, a gaseous shale oil being distilled from said preheated oil shale in said oil shale distilling chamber; and, PA1 a separator for liquefying said gaseous shale oil contained in said high-temperature gas which is blown into said separator through said gas discharge port to separate said gaseous shale oil from said gas, said separator being provided at the bottom thereof with a shale oil discharge port for discharging the thus liquefied shale oil, and being provided at the top thereof with a gas discharge port for discharging said gas after separation of said gaseous shale oil at the top thereof.
In the method (1), a fuel and the air are blown directly into the distilling furnace fed with an oil shale to cause combustion of the blown fuel, and a shale oil is distilled from the oil shale with the combustion heat of the fuel. This method, having the advantage of a high thermal efficiency for distillation, is problematic in that the quality of the resultant shale oil is degraded by the combustion waste gas and the yield of shale oil is rather low.
In the method (2), an oil shale is supplied together with a high-temperature granular heat medium, and a shale oil is distilled from the oil shale with the heat contained in the granular heat medium. This method is advantageous in that a high-quality shale oil is available. The method (2) is however problematic in that distillation requires a large quantity of high-temperature granular heat medium and a separator for separating the granular heat medium from the waste oil shale after distillation treatment, thus resulting in complicated facilities. Another problem is that, when the granular heat medium wears to a smaller particle size, separation becomes impossible with a screeen commonly employed as the above-mentioned separator.
In the method (3), a high-temperature gas as the heat medium is blown into the distilling furnace fed with an oil shale, and a shale oil is distilled from the oil shale by the heat of the blown gas. This method is advantageous in the availability of a high-quality shale oil and because the heat medium is a gas, the method does not require a separator for separating the heat medium from the waste oil shale, as in the method (2), thus requiring only relatively simple facilities.
The above mentioned method (3) for distilling a shale oil from an oil shale with a high-temperature gas as the heat medium is disclosed in the U.S. Pat. No. 4,010,092 (hereinafter referred to as the "prior art 1"), the U.S. Pat. No. 4,042,485 (hereinafter referred to as the "prior art 2"), and the U.S. Pat. No. 4,058,905 (hereinafter referred to as the "prior art 3").
The above-mentioned prior art 1 is a method which comprises employing a vertical type distilling furnace, supplying oil shale into the distilling furnace from the bottom thereof, causing continuous ascent of the oil shale through the distilling furnace toward the top thereof by means of a Rock pump provided at the bottom of the distilling furnace and discharging the oil shale from the top of the distilling furnace, and in the meantime, bringing the oil shale into counter-current contact with a high-temperature gas blown into the distilling furnace from the top thereof toward the bottom thereof, thereby distilling a shale oil from the oil shale with the heat contained in the gas. However, it is difficult for the prior art 1 to treat a large quantity of oil shale at a time because of the limited capacity of the Rock pump for forcing up the oil shale from the bottom toward the top of the distilling furnace. In addition, the contact of the oil shale with the high-temperature gas in the distilling furance, being done in counter current in the vertical direction of the distilling furnace, leads to a larger pressure drop of the gas, thus bringing about a limit in scaling up the distilling furnace.
The above-mentioned prior art 2 is a method which comprises using a vertical type distilling furnace, supplying an oil shale into the distilling furnace from the top thereof, causing continuous descent of the oil shale through the distilling furnace toward the bottom thereof, discharging the oil shale from the bottom of the distilling furnace, and in the meantime, bringing the oil shale into counter-current contact with a high-temperature gas blown into the distilling furnace from the bottom toward the top thereof to distill a shale oil from the oil shale with the heat of the gas. However, the prior art 2 is problematic in that, as the contact of the oil shale with the high-temperature gas in the distilling furnace is in counter current in the vertical direction of the distilling furnace, there is a considerable pressure drop of the gas, leading to a limit in scaling up the distilling furnace.
The above-mentioned prior art 3 is a method which comprises using a circular-shaped horizontal rotary distilling furnace, charging an oil shale into the distilling furnace, bringing the oil shale into contact with a high-temperature gas blown into the distilling furnace from the top toward the bottom thereof while moving the oil shale in rotation to distill a shale oil from the oil shale with the heat of the gas. However, the prior art 3 is problematic in that the rotation of the distilling furnace with the oil shale charged therein requires much power cost and leads to considerable leakage of the blown gas, resulting in a low distilling efficiency.
As described above, the methods comprising blowing a high-temperature gas as the heat medium into a distilling furnace supplied with an oil shale and distilling a shale oil from the oil shale with the heat of the gas, being advantageous in the availability of a high-quality shale oil and relatively simple facilities, are problematic in that the large pressure drop of the gas blown into the distilling furnace makes it impossible to employ a large-capacity distilling furnace, thus leading to a low testing efficiency of oil shale.
Under such circumstances, there is a strong demand for developing an apparatus which permits, when blowing a high-temperature gas as the heat medium into a distilling furnace supplied with oil shale and distilling shale oil from the oil shale with the heat of the gas, effective treatment of the oil shale in a large-capacity distilling furnace with a slight pressure drop of the gas blown into the distilling furnace, but such an apparatus is not as yet proposed.